The invention relates to scanners for the capturing of photographic image information from photographic media, especially scanners for the scanning of films, or to photographic printers for the projection of individual image originals (frames) contained in a photographic film onto photographic paper. In particular, the present invention relates to the control or adjustment of the focus of the projection of a photographic medium (for example a film, transparent foil with image, photographic paper with image) onto a detection element (for example a photoelectric converter such as, for example, CCD or for example a photochemical converter, such as, for example, photographic paper) in such a photographic scanning arrangement.
Focussing of the projection is normally carried out in conventional photographic scanning arrangements (scanners) or in conventional photographic copier apparatus (printers) by way of a test film or a test negative which is mounted in place of a film on a film stage and in a preselected reference position. An operator must thereby manually position the test film into the film transport arrangement or must manually position and fasten a test negative on the film stage. The focus of the test image produced with the test film or the test negative is then judged by an operator and the position of the lens adjusted until a satisfactory result is achieved.
It is now an object of the invention to provide a photographic scanning arrangement where the focus testing or focussing is simplified and reproducable.
This object is achieved with a photographic capturing device in accordance with the invention including a sample or pattern for controlling the focus of the projection and a positioning mechanism for selectively positioning the sample or pattern in a reference position for projection of the sample or pattern onto a detection means.
The capturing device in accordance with the invention can be constructed as a photographic scanner, whereby a photoelectric converter (CCD) is used as the detection means. It can also be constructed as a photographic copier (printer) whereby a photochemical converter (photographic paper) is used as the detection means.
The photographic capturing apparatus includes a light source, such as, for example, a halogen lamp or light emitting diodes. The light of the light source is preferably focussed and directed by way of light conducting elements (object lenses, lenses, mirrors, shutters, etc.) to a stage which serves for the positioning of a photographic medium to be exposed. The spectrum of the light can be changed, for example, by way of filters or by activating light emitting diodes of different color. The light transmitted by the photographic medium is preferably measured by projecting the photographic medium onto a detector, however, the reflected light can also be captured by way of a projection optics. The detection means is suited to detect the light modulated by transmission or reflection in order to so capture the image information stored on the photographic medium. As already mentioned, a CCD and photographic paper are suitable detection elements.
The photographic capturing device preferably includes an arrangement for testing the focus of the projection and especially for adjusting the focus of the projection. This arrangement in accordance with the invention includes a so called sample or pattern carrier with a sample or pattern and a positioning mechanism for moving the sample carrier into a desired reference position. The mechanism is constructed such that the sample carrier is positioned at the same reference position for each measurement process for testing the focus. It is especially preferred to position the sample carrier each time in the same object plane (plane in which the object to be exposed is located). This provides a significant advantage compared to the use of test negatives and test films. Conventional test films or test negatives can curve towards the illumination means or the detection means whereby they leave a preselected object plane. The curvature can vary in direction and extent with the surrounding temperature, the orientation of the test negative or the type of test film or test negative. The sample or pattern carrier with sample in accordance of the invention is preferably constructed to be so stiff that the sample does not curve. For example, the sample carrier is constructed as a rigid metal mesh, whereby the shape of the grid represents the sample. The sample carrier preferably has a non-flexible or non-elastic or rigid substrate which carries, forms or surrounds the sample and in this way prevents a curving of the sample. The sample or pattern which is used for the testing of the focus of the exposure is constructed with sufficient contrast that it can be recognized by the detection means at least upon focussed projection. It can be, for example, a grid, circles or other geometric shapes. The substrate which carries the sample is preferably transparent, while the sample itself is not transparent, or vice-versa, in order to achieve the strongest light/dark contrast in the plane of projection. The sample carrier is preferably positioned at the same reference position in which the photographic medium is positioned for the scanning in the conventional operation of the capturing device. The reference position is selected such that the sample is located in the preselected object plane.
In the following, the expression xe2x80x9csample carrierxe2x80x9d is used as a synonymous for the expressions sample, pattern, pattern carrier and sample carrier.
The mechanism for the positioning of the sample carrier allows the selective movement of the sample carrier to the reference position or away therefrom. The sample carrier is thereby removed sufficiently far that it does not impede the exposure of a photographic medium or the detection means. In order to achieve a defined positioning of the sample carrier at a reference position, the mechanism preferably includes positioning means, such as, for example, tracks, pivot arms, rotors. Stop means such as, for example, notches or pawls, are preferably also provided. Step motors, especially in connection with a transmission (gears) can also be provided.
The mechanism especially preferably serves a double purpose, namely the positioning of the sample carrier and the positioning of a pressure mask for the pressing of a photographic medium (film) onto a stage (film stage) at the preselected reference position. The films to be captured conventionally rest in film guides along their edges which carry no image. The films are pressed by way of a pressure mask against these edges so that the film image (frame) lies as much as possible in a defined plane, which represents the object plane in the projection geometry. Since the mask is not needed or not necessarily needed when the focus of the exposure is tested by way of the sample carrier, the mechanism is preferably constructed such that it enables the exchange between a mask and the sample carrier. For example, the sample carrier can be on a sled together with one or more masks, whereby either the mask or the sample carrier can be brought into the reference position as desired. The exchange or the positioning of the sample carrier and especially also of the mask is preferably carried out automatically and is controlled by a control arrangement.
Preferably at least one mask is positioned together with the sample carrier on a carrier member, such as, for example, a sled, so that the at least one mask and the sample carrier have a fixed position relative to one another. The carrier member is preferably guided along a preselected path, for example, by way of tracks, or by way of a rotor supported on an axis. The path preferably extends transverse to the transport direction of the film. The positioning along the path can be monitored by way of sensors. If a photoelectric converter is used as the detection means, the detection result, ie. the position of the detection sample detected with the photoelectric converter can also be used in the positioning with a control electronic.
The sample carriers, are preferably positioned between two masks in order to achieve the most compact arrangement and to have the shortest possible adjustment distance between the sample carrier and the mask. The sample carriers can thereby be positioned, for example, in mechanically necessitated spaces between the masks, for example, between fastening means (bolts) or mask frames and particularly have significantly smaller dimensions than the masks (for example smaller than a quarter of the size of a mask), in order to make the arrangement especially compact.
The sample carrier preferably includes a substrate and a sample, which is carried by the substrate. The substrate is preferably rigid and preferably has a planar surface upon which the sample is located. The substrate is constructed in particular so that it does not deform because of the heating action of the light source. A transparent material, for example, glass or transparent plastic, such as, for example, plexiglass, is preferably used for the substrate. The sample can be produced in different ways. For example, reflective or light absorbing material can be vapor deposited according to a preselected pattern onto the substrate. In order to produce the pattern, for example, the substrate can be covered except for the sample. A photo sensitive lacquer can also be applied, exposed according to the sample and thereafter fixed. Also, for example, samples can be scratched into the substrate. The depressions produced thereby can be, for example, filled with a light absorbing and/or light reflecting material.
The thickness of the material which forms the sample is preferably in the size range of the thickness of the photographic layer of a film, whereby the photographic layer represents and carries the image information. In this manner, conditions are produced in the sample carrier as they are also present in a film. The thickness of the sample is, for example, 10 xcexcm to 100 xcexcm.
The surface of the substrate need not necessarily be planar, it can also be slightly curved according to the projection geometry in order to compensate for projection errors and to enable an optimal focus adjustment. However, the substrate is preferably planar. In conventional scanners and printers, the photographic layer of the film is normally positioned such that it is directed towards the detector. Accordingly, the sample carrier is preferably positioned such that the substrate is directed towards the light source and the actual sample toward the detector.
It is a significant advantage of the invention that the sample carriers are always positioned the same so that the sample is reproducably always located in the same plane. This was not the case with the use of test films or test images because of the curvature thereof. Depending on the test image used, different focus adjustments could have deceivingly appeared optimal. This problem is overcome because of the reproducably equal positioning of the sample by way of positioning mechanism.
In accordance with the invention, the photographic capturing device includes an arrangement for the automatic testing of the focus and/or the automatic adjustment of the focus. For that purpose, the detection means is preferably a photo-electric converter arrangement onto which the carrier sample is projected. Furthermore, an output electronic and a data processing arrangement (for example a computer, CPU) is provided. The output electronic outputs from the converter arrangement the electrical signals induced by the light and guides them to the data processing arrangement. The signals which represent the image are analyzed by the data processing arrangement with a view to the focussing of the imaged sample.
Particularly, the difference in contrast is used for the assessment of the focus, ie. the light/dark difference between neighboring pixels. For this purpose, the sample is preferably constructed such that the regions cover as few pixels as possible, for example, the number of the covered pixels which have a grey value or an image value above a predetermined threshold value can be known. This number increases in an image out of focus. Sample analysis processes can also be used which are especially sensitive for the edge region of a sample. A parameter can be calculated in this manner for each picture which quantifies the focus of the image. Such a focus determination can also be carried out localized at different locations within the sample, for example, in the four corners of the image. If required, the focus assessment can also be carried out separately in the different colors. If a photochemical converter arrangement is used as the detection means, the measurement image captured by the converter arrangement can be captured (automatically) with a scanner and then analyzed by the data processing arrangement with respect to the focus of the sample. The automatic testing of the focus or adjustment of the focus can therefore be carried out analog to the embodiment with the electrical converter arrangement.
If the data processing arrangement detects a lack of focus, a warning signal can be emitted, for example, which causes an operator to readjust the focus. The testing of the focus adjustment can be carried out at regular intervals in order to thereby guarantee a continuously focussed imaging in the capturing device. The mechanism is therefore provided, for example, with a timer which, if no film is present, positions the sample carrier at regular time intervals at the reference position by way of the mechanism for testing the focus.
The evaluation of the focus is preferably combined with an automatic focussing. A control electronic is preferably provided therefor as well as an adjustment mechanism, which allows the adjustment of at least one of the following devices in their position along the optical image path: the film stage with reference position or object plane, the imaging optics and the detection means. Preferably, the imaging optics (especially an object lens, a lens or a lens system) is adjusted in its position by way of an adjustment mechanism, while the position of the stage and the detection means remains fixed. The adjustment mechanism can be combined, for example, with an electric motor, which is operated by the control electronic. The control can be carried out, for example, according to the conventional nominal/actual principle or according to a fuzzy logic principle. Preferably, the adjustment is carried out until the focus is within a preselected tolerance range which, for example, as defined by a threshold value.
In an alternative embodiment, the focus is measured at a plurality of positions (for example, 10-20) and a position of optimal focus is subsequently determined from the different points of measurement. The adjustment mechanism subsequently moves to this determined position of optimum focus. If the focus is furthermore measured in each position in different colors, it is possible to even more accurately determine the optimum position or to optimize it especially well for one color.
A carrier member on which at least one pressure mask and the sample carrier are found preferably also includes film guides respectively associated with the pressure masks. The film guides thereby guide the film in a direction which is preferably transverse to the adjustment direction of the carrier member.
In an alternative embodiment, the mechanism for the positioning of the sample carrier can also include a rotor. The latter is preferably mounted for rotational adjustment about an axis. This axis preferably extends at least substantially parallel to the direction of transport of the film or the photographic medium. At its circumference, the rotor preferably includes the sample carrier. In addition, masks (pressure masks) for different film formats can be provided along the circumference. An individual pressure mask or a sample carrier can be selectively guided to the reference position for exposure by rotational adjustment of the rotor.
Further features of the invention are disclosed in the following detailed description of different preferred embodiments. Features of different embodiments can be combined with one another. Equal reference numbers define, unless otherwise indicated, equal parts or parts of similar function.